Rate limiting middleware

[MrImmortal09]

Context

Every write endpoint needs rate limits to prevent abuse. Use Upstash Ratelimit or a simple in-memory + Redis fallback.

Acceptance criteria

• lib/ratelimit.ts exports a limit(key, config) helper
• Applied to: magic link requests, sign-up, recovery requests, contact form, job posting, report submission, avatar upload
• Returns 429 with Retry-After header on breach
• Logged to AuditLog when a user consistently hits limits

Depends on #1.

[Ewan-Dkhar]

/assign

[mini-walkerx]

@Ewan-Dkhar You are already assigned to 2 active issues across repositories. Please finish those before taking on more.

[MrImmortal09]

@Ewan-Dkhar here u go

[MrImmortal09]

Open a PR within next 3 hrs.

[mini-walkerx]

🔗 @Ewan-Dkhar opened PR #45 for this issue and has been auto-assigned.

[Ewan-Dkhar]

/unassign

[mini-walkerx]

✅ Successfully unassigned @Ewan-Dkhar. Waitlist queue triggers to be processed here.